Recently, the American Institute of Chemical Engineers (AIChE), in conjunction with the U.S. Department of Energy (DOE), published Vision 2020: 2000 Separations Roadmap. Adler S., Beaver E., Bryan P., Robinson S., Watson J., Vision 2020: 2000 Separations Roadmap, American Institute of Chemical Engineers, New York, 2000. This document outlines technical barriers and research needs for the foreseeable future in the areas of adsorption, extraction, crystallization, membranes, bioseparations, and distillation. Prominent among the most important research needs and barriers for distillation are: 1) the need for a better understanding of mass transfer and multiphase flow in both trayed and packed columns, 2) the lack of accurate real stage efficiency models for these types of columns, and 3) the fact that nonequilibrium column models lack accuracy, generality, and ease of use. Rate-based calculations for trayed and packed columns offer process engineers a more rigorous and reliable basis for assessing column performance than the traditional equilibrium stage approach, especially for multicomponent separations. While the mathematics, thermodynamics, and transport-related physics upon which nonequilibrium separations theory is founded are generally true, it is also true that rate-based simulations today suffer from a serious weakness—they are ultimately tied to underlying equipment performance correlations with questionable predictive capability. In the case of packed columns operated countercurrently, correlations are required for the liquid-side and vapor-side mass transfer coefficients, kx and ky, respectively, for the specific area participating in mass transfer, am, for the two-phase pressure drop, (Δp/z)2φ, and for the flood capacity of the column. In particular, it is generally well-known that packing mass transfer correlations available in the public domain are unreliable when they are applied to chemical systems and column operating conditions outside of those systems and conditions used to develop the correlations in the first place.
Therefore, there is a need for dependable, dimensionally consistent, correlating expressions for the mass transfer related quantities kx, ky, and am for packed columns.